This invention relates to a beverage brewing apparatus, and more particularly, to apparatus for rapidly preparing cup size quantities of hot coffee or the like from a freshly ground charge of beverage material without variation in the quality of the beverage.
Beverage brewing apparatus for preparing single cup quantities of beverages from beverage material is well known in the prior art. For example, U.S. Pat. No. 3,349,690 issued to William Heier discloses one construction for such a brewing apparatus.
Referring to FIG. 1 on the application drawings, the basic construction and brewing cycle of a prior art apparatus will be described.
A frame 1 of the apparatus supports a vertically movable open-bottom cylinder 2 which has the bottom opening covered by a filter member 3. A vertically movable piston 4 is disposed within cylinder 2 and relative movement between cylinder 2 and piston 4 is created by operation of cam member 5 driven by motor 6. One end opening of a duct 7 is connected with water tank 8 through electromagnetic valve 9, this end opening being closely placed above the upper opening of cylinder 2 to supply hot water into cylinder 2. A brewing cavity 10 which is generally reciprocable horizontally between a brewing position D and a rest position A is placed beneath the cylinder 2 and sealed with the lower portion of cylinder 2 in the brewing position D.
The prior art apparatus is also provided with a coffee hopper 11 which has an outwardly flaring mouth 11a positioned to receive a charge of coffee from outlet spout 12a of canister 12. The ground coffee fills canister 12 which is provided with suitable feed means to deliver a predetermined quantity of fresh ground coffee into hopper 11 at a point prior to the start of the brew extracting operation.
In this apparatus, brewing cavity 10, at the start of a brewing cycle initiated by a coin operated switch for example, moves horizontally toward brewing position D from rest position A to a place beneath the bottom opening of cylinder 2. During this horizontal movement, the ground coffee is supplied into the brewing cavity 10 through coffee hopper 11 at the position indicated by "C" in FIG. 1. When brewing cavity 10 is properly aligned beneath the cylinder 2, due to the operation of cam member 5, cylinder 2 moves downwardly into tight engagement with cavity 10. This forms a chamber which is filled with hot water supplied through duct 7. Thereafter, piston 4 moves downwardly to force the water through filter member 3 into the ground coffee in cavity 10 and through an outlet conduct 13 to a cup 14 placed at a dispensing station. Thereafter, the brewing cavity 10 containing the spent coffee grounds is moved to its rest position A and the grounds in the brewing cavity 10 are thrown away at the ground dumping position which is reached before rest position A, this position being indicated by "B" in FIG. 1. When the brewing cavity 10 is returned to its rest position A, one brewing cycle has been completed.
During the brewing cycle, the brew extraction time of beverage within brewing cavity 10 is influenced by the desired strength of the brewed beverage, i.e., the extraction efficiency of the beverage material is dependent upon the brew extraction time. Therefore, several improvement ideas to improve the extraction efficiency are possible. The time of one brewing cycle could be extended or movement of the piston horizontally shifting cavity 10 may be temporarily stopped in a midway position of the brewing cycle. However, generally customers using the apparatus are unwilling to wait for service more than a few moments after they have deposited their coin.
In addition, as shown in FIG. 2, the prior art proposes that a seal element 15 be disposed on the outer peripheral portion of piston 4 to tightly seal between the outer peripheral surface of piston 4 and inner surface of cylinder 2. Thus, during the brewing cycle, the hot water filling cylinder 2 is easily and quickly passed through the ground coffee G in the brewing cavity 10. However, if piston 4 is moved quickly downwardly, the pressure within the interior of cylinder 2 which is defined between the inner surface of cylinder 2 and piston 4 is rapidly raised, thereby causing problems. That is, lip portion 15a of seal element 15 which normally contacts with the inner surface of cylinder 2 is spread out by the high pressure and strongly pushed against the inner surface of cylinder 2. This deformation of lip portion 15a is shown by dotted line in FIG. 2(b). Therefore, the rubbing force of seal element 15 against cylinder 2 is increased until finally seal element 15 becomes damaged. Also, large loads acting on piston 4 through seal element 15 finally detrimentally influence the operation of driving motor 6.